The present invention relates to a film forming apparatus such as an ion-beam sputtering apparatus in which a device of holding a substrate such as a disk in a film forming chamber and a device of delivering a substrate are improved, the quantity of treatment per unit time (throughput) is improved, an outside line of carrying a substrate is simplified, and the deposition of film in a load lock chamber is prevented.
A conventional film forming apparatus is configured as shown in FIG. 1 which is a schematic plan view of the apparatus. In this drawing, reference numeral 41 designates a film forming chamber in which a film is formed on a disk 43 located at a film forming position 42; 44, two load lock chambers provided with their one sides disposed adjacent to the film forming chamber 41 through inner square gate valves 45; 46, outer square gate valves provided on the other sides of the respective load lock chambers 44; 47, pivots uprightly provided in the respective load lock chambers 44; 48, carrying arms supported by the respective pivots 47; and 49, an exchange position at which a disk 43 is mounted or demounted.
With respect to one of the load lock chambers 44, the outer gate valve 46 is opened, the forward end portion of the carrying arm 48 is moved into to the exchange position 49, a disk 43 is set to the forward end portion, the disk is carried into the load lock chamber 44, the outer gate valve 46 is closed, and the load lock chamber 44 is exhausted into a vacuum state. Then, the inner gate valve 45 is opened, and the disk 43 is carried into the film forming position 42 to perform film formation.
In this duration, with respect to the other one of the load lock chambers 44, another disk 43 before subjected to film formation is carried into the other load lock chamber 44 in the same manner as described above, and the load lock chamber 44 is exhausted into a vacuum state.
After completion of the above-mentioned film formation, the former disk 43 is returned into the one load lock chamber 44, the inner gate valve 45 is closed, the outer gate valve 46 is opened, the disk 43 is returned into the exchange position 49, the disk 43 after subjected to film formation is taken out, and another disk 43 before subjected to film formation is set.
In this duration, the disk 43 in the other load lock chamber 44 is being subjected to film formation in the film forming position 42. The above-mentioned procedure is repeated so that disks are subjected to film formation successively.
In the case of the conventional film forming apparatus, the pivots 47 of the carrying arms 48 are provided in the load lock chambers 44 respectively. Accordingly, the volume of each of the load lock chambers 44 becomes large, so that vacuum exhausting time becomes long. Thus, there arises a problem that the quantity of treatment per unit time is reduced. Further, since the inner gate valve 45 is kept opened in the duration of film formation, there arises another problem that film may be deposited on a seal surface of the inner gate valve 45 and an inner surface of the load lock chamber 44.
A conventional substrate holding device of a film forming chamber of a conventional film forming apparatus is configured as shown in FIGS. 2 and 3. In the drawings, reference numeral 31 designates an up/down movable hollow main shaft; 32, a hollow arm shaft rotatably supported in the inside of the main shaft 31 through a bearing 33; 34, a drive shaft rotatably supported in the inside of the arm shaft 32 through a bearing 35; 36, a carrying arm formed integrally with the arm shaft 32 at an upper end thereof so as to extend in the horizontal direction; 37, a rotating shaft rotatably supported on an end of the arm 36 through a bearing 38; 39, a deposition preventing plate integrally formed with an upper end of the rotating shaft 37; and 310, a substrate such as a disk mounted on the deposition preventing plate 39.
Reference numeral 311 designates a small pulley fixed on an upper end of the drive shaft 34; 312, a large pulley fixed to a peripheral surface of the rotating shaft 37; 313, a belt wound around both the pulleys 311 and 312; 314, holders provided radially at a central portion of the rotating shaft 37 and rotatably supported at their central portions by pivots 315 respectively; 316, springs for inward urging the lower portions of the respective holders 314; and 317, holding pawls projectingly provided at the upper outside portions the respective holders 314 so as to push the inner circumferential edge portions of the substrate 310.
Reference numeral 318 designates a rotary shaft; 319, a support rod formed integrally with the rotary shaft 318 so as to obliquely extend from the lower end of the rotary shaft 318; and 20, a mask fixed on the forward end of the support rod 319 for covering the holders 314 so as to prevent a film from adhering onto the holders 314. Reference numeral 321 designates a cooling water path formed so as to communicate with the arm shaft 32 and the arm 36 for absorbing heat due to sputtering particles.
Next, the operation will be described. In a load lock chamber, the respective lower portions of the holders 314 are urged outward against the spring 316, the substrate 310 is mounted on the deposition preventing plate 39, and the above-mentioned urging is released so that the substrate 310 is held by the holding pawls 317. Then, the carrying arm 36 is rotated by means of the arm shaft 32 so as to carry the substrate 310 into the film forming position. The main shaft 31, the arm shaft 32, the drive shaft 34, and the like are pushed up so that the holding pawls 314 are disposed below the mask 320. The substrate 310 is rotated by rotation of the drive shaft 44 through the small pulley 311, the belt 313, the large pulley 312, the rotating shaft 37, and the deposition preventing plate 39, so that film formation is performed.
After completion of film formation, the substrate 310 is carried into the load lock chamber in the reverse process to the foregoing one.
In the foregoing conventional holding device, there have been various problems as follows.
(1) The main shaft 31, the arm shaft 32, and the drive shaft 34 constitute a triple shaft structure and therefore the rotation and airtight mechanisms are complicated.
(2) The belt 313 is disposed above the carrying arm 36 so that the thickness is large, and a gate valve of the load lock chamber is required to have a large opening so that the cost becomes high. Further, the volume of the load lock chamber becomes large so that the vacuum exhaust time becomes long.
(3) It is necessary that the deposition preventing plate 39 is subject to frequent maintenance because it is a member on which the quantity of film deposition is largest. The deposition preventing plate 39, however, is required to be disassembled together with the rotating shaft 37 because the former is formed integrally with the latter, so that the disassembling work is troublesome.
(4) Further, in the case of a PMMA disk to be used as a laser disk, the radial structure has a directional property and the central portion of the disk is pressed by means of the radial holding pawls 317, so that the disk is apt to be broken.
(5) In the case of provision of a plurality of load lock chambers and carrying arms 36, it is necessary to use complicated triple shaft structure of the same number as that of the carrying arms 36.
FIG. 4 shows a conventional delivering device of a film forming substrate of a conventional film forming apparatus, by which a substrate to be subjected to film formation is delivered in a load lock chamber to a carrying arm. In this drawing, reference numeral 51 designates a film forming chamber in which film formation is performed; 52, a load lock chamber provided at one side of the film forming chamber 51 through a gate valve 53; 54, a pivot led into the film forming chamber 51 through a magnetic fluid seal 55; 56, an arm servomotor for rotating the pivot 54; 57, a carrying arm fixed to an upper end portion of the pivot 54; and 58, a C-shaped support portion formed at a forward end portion of the carrying arm 57 so as to move between a delivery position of the load lock chamber 52 and the film forming chamber 51 through the pivot 54 and the carrying arm 57 by rotation of the arm servomotor 56.
Reference numeral 59 designates a ball screw rotated by a servomotor 510 for up/down movement; 511, an up/down moving plate thread-engaged with the ball screw 59 so as to be moved up/down by the rotation of the ball screw 59; 512, an up/down moving shaft planted on the up/down moving plate 511 and led into the load lock chamber 52; 513, a tray mount fixed to an upper end of the up/down moving shaft 512 and provided in the load lock chamber 52; 514, bellows provided between the up/down moving plate 511 and the load lock chamber 52 so as to surround a base portion of the up/down moving shaft 512; 515, a tray mounting a substrate 516 thereon and mounted on the mount 513; and 517, a cover of the load lock chamber 52.
The movement of the substrate 516 will be described below.
First, the cover 517 of the load lock chamber 52 is opened in the condition in which the gate valve 53 is closed, the substrate 516 is mounted on the tray mount 513 located above, and the cover 517 is closed so that vacuum exhaustion is performed. Then, the gate valve 53 is opened, the arm servomotor 56 is rotated so that the support portion 58 of the carrying arm 57 is led into the delivery position of the load lock chamber 52. In the tray mount 513, an opening is formed to make it possible to move the carrying arm 57. In this condition, the up/down moving servomotor 510 is driven so that the tray 515 is moved down through the ball screw 59, the up/down moving plate 511, the up/down moving shaft 512 and the tray mount 513 so as to be mounted on the support portion 58.
Then, the carrying arm 57 is rotated reversely by the reverse rotation of the arm servomotor 56, so that the support portion 58 moves into the film forming chamber 51.
In the case of the conventional delivering device, the servomotors 56 and 510 are used for rotating the carrying arm 57 and for up/down moving the tray mount 513, respectively. Accordingly, not only the cost is high because of use of the two motors 56 and 510 but the control is complex because it is necessary to link the respective operations of the two motors 56 and 510 with each other.
Further, because the bellows 514 is used for up/down moving, the inner surface area of the load lock chamber becomes large. Accordingly, a long tome is required for exhaustion up to a high vacuum region.
Furthermore, there are many airtight points in the up/down moving operation portion. Thus, there arises a problem that maintenance such as periodic exchange of the seal material and the bellows 514 is required.
FIG. 5 shows still another film forming apparatus to form a thin film such as an aluminum thin film. In the drawing, reference numeral 21 designates a film forming chamber in which a thin film of, for example, aluminum is formed onto a substrate 22; 23, a load lock chamber provided through an inside gate valve 24; 25, an outside gate valve provided outside the load lock chamber 23; 26, a turbo molecular pump provided in the load lock chamber 23 through a pump-side gate valve 27; 28, a rotary pump connected to the turbo molecular pump 26 through a pump-side valve 29; and 210, a carrying arm.
The outside gate valve 25 is opened so that the substrate 22 is mounted on the arm 210, the valve 25 is closed, and the load lock chamber 23 is exhausted by means of the rotary pump 28 and further exhausted into high vacuum by means of the turbo molecular pump 26. On the other hand, the film forming chamber 21 has been exhausted into high vacuum by means of the turbo molecular pump in advance. In the state where the degree of vacuum of the load lock chamber 23 has reached the same value as that of the film forming chamber 21, the inside gate valve 24 is opened, the substrate 22 is carried into the film forming chamber 21 by means of the arm 210, and the valve 24 is closed so that film formation is performed.
After completion of film formation, the inside gate valve 24 is opened, the substrate 22 is carried into the load lock chamber 23, the valve 24 is closed, the outside gate valve 25 is opened, the substrate 22 is discharged, another substrate 22 which is to be subjected to film formation next is carried into the load lock chamber 23, the outside gate valve 25 is closed, the load lock chamber 23 is exhausted by means of the rotary pump 28 and the turbo molecular pump 26, and the foregoing film forming operation is repeated.
Experimentation was carried out to form thin films of aluminum on substrates to obtain a stable high reflection factor. Such a result as shown in FIG. 6 was obtained when the rate of film formation was 3000 .ANG./min. That is, in order to obtain a reflection factor not lower than 82.5%, it is necessary to make the film forming chamber be high vacuum not lower than 6.times.10.sup.-5 Torr.
There is a problem in that although it is possible to exhaust the film forming chamber 21 of FIG. 5 into high vacuum of 1.times.10.sup.-7 Torr because exhaust is performed by using the turbo molecular pump, it is necessary to keep the load lock chamber 23 in high vacuum so that the state of vacuum of the film forming chamber 21 does not become lower than the above value of 6.times.10.sup.-5 Torr when the inside gate valve 24 is opened, and it is therefore necessary to use not only the rotary pump 28 but also the expensive turbo molecular pump 26, so that the equipment cost becomes extremely expensive.